1. Field of the Invention
The field of the present invention is laser beam control systems, particularly systems that both control direction of the laser beam and provide wavefront correction.
2. Background
Laser beam control systems have many disparate applications, such as directed energy weapons, both lethal and non-lethal, LIDAR and beacons, countermeasures, remote chemical sensing, target illumination, and micromachining. Among these applications, the high energy laser (HEL) beam control systems are used mainly in directed energy weapons. Beam control in HEL systems is rendered more challenging since such systems are often required to direct the HEL to a target across large distances, thus requiring adaptive optics to correct for atmospheric turbulence and aerosol effects.
Current HEL beam control systems generally have high power optical trains containing more than a dozen mirrors. Having so many components in the optical train adds to the size, weight, and complexity of the control system. However, as the need for mobile deployment of directed energy weapons increases, the beam control systems necessarily need to be reduced in size, weight, and complexity, without sacrificing sophistication.
HEL beam control systems typically use two illuminators, one to track the hard body of the target (called the “target illuminator”) and the other for wavefront sensing (called the “beacon illuminator”). The target illuminator is usually a broader beam, and it is usually directed to a large portion of the target, or sometimes the entire target, to track features of the target, locate and select an aimpoint on the target, and maintain a stable line of sight to the target. The beacon illuminator is a beam directed toward the aimpoint, or alternatively ahead of the aimpoint to correct for distances and target velocity. The beacon illuminator is usually a beam at a wavelength different from the HEL in order to enable distinguishing the two beams. The return from the beacon illuminator is sent to an adaptive optics system to measure the wavefront error resulting from the flow field and atmospheric turbulence between the HEL source and the target. Such two illuminator systems, while functional, are costly, heavy, and complex.
HEL beam control systems have also been traditionally blind. In existing systems, the target is tracked using a different wavelength than the HEL beam and the internal alignment system is used to infer the HEL boresight relative to the target without any measurements of the actual HEL beam position on the target. Simply put, this arrangement slows down and potentially decreases precision of targeting.